The goal of this research proposal is delineation of primary genetic defects which are responsible for dentinogenesis imperfecta type II (DGI- III) and type III (DGI-III) and the autosomal dominate local hypoplastic form of amelogenesis imperfecta (ADAI). Dentinogenesis imperfecta (DGI) and amelogenesis imperfecta (AI) are inherited disorders of both the primary and secondary dentitions which affect dentin and enamel formation, respectively. The genetic linkage of DGI- II in a number of multi- generation families has been studied and place this gene locus on human chromosome 4 in the region 4q21-q23. Furthermore, a linkage study on a DGI-III kindred with juvenile periodontitis (JP) has also suggested that this disease may be linked to the long arm (q) of human chromosome 4. Furthermore, the autosomal dominate local hypoplastic form of AI has also been recently linked to a 15.2 cM region of human chromosome 4 in the region 4q11-4q13. The proposal is based on the following hypotheses: 1, that mutations within one of the human dentin matrix proteins, dentin matrix 1 (DMP1), dentin sialoprotein (DSP) or dentin phosphoprotein (DPP), genes localized to 4q21-q23, cause DGI types II and/or III; and 2, that mutations within the human ameloblastin (AMBN) gene localized to 4q21 causes the local hypoplastic form of ADAI. To test these hypotheses, a human third molar cDNA library will be constructed in order to isolate the human cDNAs for DMP1, DSP and DPP and Ambn. These human cDNAs will be used to facilitate screening of human P1 or PAC genomic libraries for DMP1, DSP, DPP and AMBN genomic clones. In parallel, studies will be initiated to regionally localize DSP and DPP genes on human chromosome 4 using fluorescence in situ hybridization. Refined linkage studies will be performed to further establish linkage of DGI-III to human chromosome 4 q21-q23 markers. Once the human sequences for DMP-1, DSP, DPP and AMBN have been determined, mutational analysis of these genes will be initiated using available DNA samples of both DGI-II and III (DMP1, DSP, DPP) and ADAI (AMBN) kindreds.